It has been known for many years to measure and record the quantity of milk obtained from an animal during each milking. It is also well known to analyse the milk quality and/or composition by sensing certain properties of the milk, such as electrical conductivity, somatic cell count, temperature, light absorption or transmission characterics which may be indicative of fat content for example, and protein content. The results of the quantity measurements and analysis of the milk can provide important information about the health and well-being of an animal, and is of valuable assistance to herd management. For example, mastitis and other infections may be detected at an early stage before milk quality become seriously impaired, automatic separation of foremilk can be implemented, the course of the lactation period can be automatically monitored, and appropriate amounts of food and feed concentrates can be calculated to ensure a well balanced diet, all of these factors making important contributions to efficient milk production in terms of yield and quality.
A milk meter currently manufactured and marketed by DeLaval International AB is based on the milk meter described in GB-A-2113856A and includes a metering chamber defined within a measuring container supported by a strain gauge. The chamber has a milk inlet and a milk outlet which is controlled by a valve so that the metering chamber is repeatedly filled and emptied during the milking of an animal. The milk outlet valve is opened when a predetermined amount of milk has collected in the chamber, the predetermined amount being dependent on the rate of milk flow into the metering chamber, and the valve being closed again after a certain time. A container for collecting a sample may be attached to the milk meter to receive a portion of the milk discharged from the metering chamber each time it is emptied. This known milk meter provides an accurate measurement of the milk quantity, but analysis to determine the quality and/or composition of the milk has to be carried out separately on the collected sample after completion of milking.
In U.S. Pat. No. 3,841,756 there is described a milking parlour in which there is provided for each milking stall a milk analysing unit consisting of a container in which all the milk obtained from an animal during a milking is collected and the weight of the milk is measured. Inserted in the container of the analysing unit are a leukocyte sensor and a butterfat sensor, the former sensor having electrodes for sensing the electrical conductivity of the milk, and the latter sensor having an infrared light transmitter and a photocell for measuring the infrared light absorption property of the milk. The results of the quantity, leukocyte content and butterfat content measurements are recorded in the form of a printout. This analysis unit provides information on the milk quality/composition as well as the quantity of milk let down by each animal, but the ability to produce just one set of values for each milking severely limits the extent to which the recorded data can be utilised. In addition to changes which may occur from one milking to the next, variations in milk quality/composition over the course of a single milking can reveal information of valuable significance to herd management decision making. Furthermore, comparison of data obtained for milk collected from respective udder quarters can be helpful also, such as in the detection of subclinical mastitis.
EP-A-0385539 describes an automatic milking apparatus in which the teat cups are connected to respective milk meters. Each milk meter has a measuring chamber with a milk inlet and a milk outlet controlled by respective valves. The inlet and outlet valves are controlled so that the measuring chamber is repeatedly filled to a predetermined level and emptied, the number of filling and emptying cycles being counted by a computer to determine the quantity of milk obtained from each quarter of the udder of the animal. Each milk meter includes an electrical conductivity sensor for detecting milk effected by mastitis, the computer controlling a valve downstream of the metering chamber so that infected milk discharged from the metering chamber is diverted away from the main milk tank. This arrangement is useful for separating milk of unacceptable quality, but there is no provision for recording data relevant to the milk quality/composition to permit comparison over the course of a milking and from one milking to the next milking.
EP-A-0564023 describes a milking plant including milk meters of essentially the same form as described in EP-A-0385539, but there is no conductivity sensor or diverter valve for separating infected milk. Downstream of the milk meter is a sampling device. Filling and emptying the measuring chamber of the milk meter is repeated just a few times during one milking. During at least a selected number of emptying phases a small fraction of the milk discharged from the measuring chamber is diverted to the sampling device so that e.g. about 1% of the milk obtained from the cow is collected in a collecting element. With this arrangement a single sample is collected for a complete milking and it is not possible to compare analysis results for samples taken at particular stages of successive milkings or at different stages of the same milking.
There is disclosed in EP-A-0665434 and EP-A-0666475 milking installations in which a milk analyser is located downstream of a milk quantity meter in a milk line between a milk pump and a milk tank. A display screen displays the milk quantity determined by the quantity meter as well as the fat content and the albumin content determined by the milk analyser. This equipment is not able to discriminate between property values relating to milk quality or composition at discrete stages of a milking of a animal.